The present invention generally relates to copying apparatuses having automatic document feeders, and more particularly to a copying apparatus provided with an automatic document feeder and an optical scanning device wherein a document feeding direction of the automatic document feeder on a contact glass of the copying apparatus is opposite to a scanning direction of the optical scanning device.
The conventional copying apparatus is provided with a contact glass having such a size that a document of size A3 can be placed thereon sideways, due to reasons such as the frequency with which the documents of different sizes are copied, the design of the copying apparatus and the ease with which the copying apparatus may be operated. Normally, a maximum size of the document which can be copied is size A3, but in most cases, the documents which need to be copied are smaller than size A3. In addition, if the document were to be fed along a direction perpendicular to a longitudinal direction of the document, that is, along the shorter side, it would be necessary to provide means for feeding the document across the longer side of the document to ensure smooth feeding. Furthermore, it would be difficult to accurately guide the document along the shorter side.
On the other hand, when the document is fed along the longitudinal direction of the document, the means for feeding the document only needs to be provided across the shorter side of the document, and a more accurate guidance of the document is possible along the longer side of the document. For these reasons, the copying apparatus is designed so that the document having the maximum size is fed along the longitudinal direction of the document and placed on the contact glass sideways.
Hence, in virtually all of the copying apparatuses, the copying operation is carried out by feeding both the document and the copying paper from the right to left along the longitudinal direction of the contact glass, for example, so as to simplify the construction. In such a copying apparatus, it is easiest from the point of design to make an optical scanning device scan the document along a scanning direction by moving from the left to right. In this case, the document is set on the contact glass by aligning the left side of the document to a reference line or position of the contact glass. Usually, the reference line is the left side of the contact glass.
When automatically feeding the document by use of an automatic document feeder, the document cannot be set correctly on the contact glass unless each document is fed to such a position that the left side of the document becomes aligned to the reference line of the contact glass, regardless of the size of the document. For this reason, a time it takes for the automatic document feeder to set a document on the contact glass from a time when the feeding of the document may be started (hereinafter simply referred to as a document setting time) must be set to a document setting time for the document having the maximum size which is usually size A3, regardless of the size of the document which is actually fed and copied. As a result, when the automatic document feeder feeds documents having sizes smaller than the maximum size, there is an unnecessary time loss in that the document setting time is longer than what is actually required. Therefore, there is a problem in that a number of documents which can be copied per unit time by use of the automatic document feeder is small.